In the undercarriages of railway vehicles it is common to provide bogies or trucks which can be pivotal about an upright axis relative to the vehicle body or chassis; each bogie can carry a pair of axles, each axle having a pair of wheels adapted to run upon the track on respective rails. The two wheels and the common axle can form a wheel set.
Thus bogies or trucks which have at least two wheel sets, which can be resiliently suspended in the bogie or truck, can be provided in such fashion as to permit axial displacement of the wheel sets within the bogie or truck frame to facilitate pivoting of the bogie on the vehicle.
Such bogies or trucks are disclosed, for example, in German patent documents (open applications) Nos. 20 29 329 and 24 19 989.
While these systems have been found to be significant improvements over earlier arrangements in which some axial or transverse movement of the wheel sets in the bogie frames was not permitted, they have not hitherto been capable of satisfactorily ensuring high stability on railway straightaways and turns at high speeds, for example 150 km per hour and more, especially 250 km per hour and up.